Control of variable-stroke power hammers



Jan. 17, 1967 G. J. GENDRON CONTROL OF VARIABLE-STROKE POWER HAMMERSFiled April 15, 1964 4 Sheets-Sheet 1 wm wm /IIIIIIIIIIIIIIIIIII ul/lJan. I7,' 1967 G. J. GENDRON CONTROL OF VARIABLE-STROKE POWER HAMMERSFiled April 15. 1964 4 Sheets-Sheet 2 7 G. J. GENDRON ,2 3,

CONTROL OF VARIABLE-STROKE POWER HAMMERS I Filed April 15, 1964 4Sheets-Sheet s Jan. 17, 1967 G. J. GENDRON CONTROL OF VARIABLE'STROKEPOWER HAMMERS Filed April 15, 1964 4 Sheets$heet 4 will lillIILlF.

United States Patent 3,298,447 CONTROL OF VARlABLE-STROKE POWER HAMMERSGeorge J. Gendron, Oradell, N.J., assignor to Raymond InternationalInc., New York, N.Y., a corporation of New Jersey Filed Apr. 15, 1964,Ser. No. 359,911

9 Claims. (Q1. 173---8) This invention relates to hydraulic powervhammers, and more particularly to the control of the length of thestroke thereof under varying conditions of use.

The invention is particularly well adapted for use in connection withdifferential types of hydraulic hammers, that is, those in which, duringthe working stroke, the spaces both above and beneath the piston arefilled with liquid under pressure, but the space beneath is partiallyoccupied by the piston rod, so that the total pressure applied above thepiston is greater than that on the underside, by reason of the fact thatthe area of the underside of the piston is less than the area on theupper side by an amount equal to thecross-sectional area of the pistonrod. The invention under some circumstances may also be desirable foruse .in connection with the so-called doubleacting types of hydraulicpower hammers.

Such power hammers are frequently used for purposes such as pile drivingand the conditions are generally such that the length of the workingstroke may be adjusted to a predetermined value. In driving piles, pilecores or mandrels therefor, a so-called cap block or cushioning means isplaced on the upper end thereof and the hammer is suspended in suchmanner that it will be lowered successively as the pile or the like isdriven, so that very effective working strokes can be obtained withoutthe necessity of successively adjusting the lengths of the stroke.

However, if a power-driven hydraulic hammer is to be used to rapidlyforce a mass of cementmix or the like down into or through a pile shellfor forming, for example, a pile with a bulbous lower end in accordancewith one of the uses of such hammers as contemplated by this invention,then it is necessary to vary the length of each working stroke, becausethe point at which the hammer ram meets heavy resistance at the bottomof each stroke may vary considerably. Hydraulic power hammers controlledin accordance with the present invention are well adapted to meet theseand similar conditions and same are also adapted to be utilized forpurposes such as forging heavy metal members, the thickness or height ofwhich diminishes with each successive stroke so that the hammer, ifsuspended in fixed position, should have a working stroke of varyinglength, depending on the extent to which the workpiece or pieces becomecompressed as the forging operation proceeds. In the usual power hammerconstructions, mechanical valves are provided to be actuatedautomatically to cause reversal of the piston movement at the end ofeach stroke, but such automatically operated valves are not welladaptedfor any form of automatic variation of the length of the workingstroke, and so far as is known, there has heretofore been nosatisfactory available method for variably controlling the stroke tomeet conditions such as above referred to.

Furthermore, with such mechanically operated valve arrangements, therewill necessarily be some premature valve action and consequentthrottling and reduction of the energy of the blow. Althoughsucharrangements are designed to restrict this difliculty to a minimum, withthe present invention, the nature of its operation is such as toeliminate any such premature valve action. 7

The present invention provides a solution to this problem preferably byway of utilizing the so-called water hammer effect which occurs in thehydraulic fluid above the piston just following the moment the hammerstrikes "ice its blow. That is, at thev moment of impact, the violentdeceleration of the fast-moving column of hydraulic fluid accompanyingthe piston on its downward stroke, has the effect of momentarily causingsharply increased pressure, due to the kinetic energy of the movingliquid. express-ion water hammer as used herein is intended to beapplicable whether the hydraulic fluid used is actually water, oil orsome other appropriate liquid.) According to the present invention, thekinetic energy of such water hammer is utilized to actuate control valvemeans so as to release the hydraulic pressure above the piston promptlyfollowing the moment of impact, even though each succeeding stroke ofthe piston may dilfer in length from the preceding one.

The apparatus of the invention is also inherently capable of thusactuating the control valve, even in cases where the impact or blow ofthe hammer is not so severe as to cause the water hammer effect, such asin cases described below in connection with FIG. 3, or at times when thehammer is being started and when on its first upstroke it is necessaryto release obstructing pressure which would otherwise occur above thepiston. In such cases the system of the present invention using positivedisplacement pumps in a hydraulic system of a closed nature, results inthe power source continuing to supply fluid against the immobile piston,thereby raising the general level of the system pressure to actuate theabove-mentioned control valve means so as to release the hydraulicpressure above the piston promptly following the impact, or the desiredtermination of the downstroke. Thus while the invention makes possibleautomatic variation of the length of the working stroke responsive tothe water hammer effect, it still permits normal starting of the hammerand normal full stroke operation when the impacts are not such as tocause a water hammer.

Various further and more specific objects, features and advantages ofthe invention will appear from the description given below, taken inconnection with the accompanying drawings, illustrating by way ofexample preferred forms of the invention.

FIG. 1 is an elevational view of the upper portions of a differentialhydraulic hammer assembly, this view showing the disposition ofcertainof the mechanical parts as arranged to provide for the featuresof the present invention;

FIG. 2 is a horizontal sectional view taken approximately through themid-portion of FIG. 1 and further showing somewhat schematically anappropriate disposition of various of the mechanical parts and devicesas arranged to provide for the present invention;

FIG. 3 is a schematic diagram of a hydraulic circuit arrangement inaccordance with one embodiment of the present invention and showing,more particularly the relationship of the parts during the downstroke ofthe piston in a differential hydraulic hammer and showing therelationship of a cycling valve therefor operable hydraulically in onedirection and by cam means in the other direction;

(In this diagram, as well as in the other diagrams referred to below,American Standards Association symbols are used for showing various ofthe hydraulic valve and other parts of the hydraulic circuit.)

FIG. 4 is a schematic diagram similar to that of FIG. 3, but showing thehydraulic circuit in accordance with another embodiment of theinvention, wherein a main cycling valve is provided for hydraulicoperation in both directions, a supplemental or pilot valve beingprovided, operable hydraulically in one direction and by cam means inthe other direction, this diagram illustrating the condition of thecircuit during the downstroke of a differential hydraulic hammer;

(The

FIG. 5 is a'view like FIG. 4, but illustrating the relationship of theparts of the hydraulic circuit during the upstroke of the hammer;

FIG. 6 is a view corresponding to FIG. 3, but illustrating anotherembodiment of the invention as applied to a so-called double-acting typeof hydraulic hammer, as contrasted with the differential hammer of theprevious diagrams; and

FIG. 7 is a vertical sectional view somewhat diagrammatically showing apossible disposition of the mechanical parts of a hydraulic hammerassembly embodying the invention and in a form adapted for useinternally of a casing and pile shell as driven into the ground, FIG. 7Aillustrating the lower portions of the assembly, of which FIG. 7 showsthe upper portions.

It will be understood that, while in the drawings and the followingdescription, the cylinders and pistons are shown and described inpositions so that the active or working stroke will be downward and thereturn stroke upward, yet these hammers may, of course, be mounted orused in any desired position or orientation and thus terms such asdownstroke and upstroke and upper and lower are herein used only forconvenience and not as limitations.

Referring now to the drawings in further detail, in FIG. 1 the cylinderof a differential hydraulic hammer is indicated at 12, suitablyconnected, by known means as at 13 at its upper end, to an uppersupporting plate structure 14, which in turn is carried by a suitableknown form of sheave housing 15, containing for example a pair ofsheaves 16, for cables 17, used in suspending the hammer in operatingposition.

The assembly may also include a lower or base plate 13, through anaperture 19 at the center of which the cylinder 12 extends downwardly,the piston rod for the hammer being indicated at 20, the lower endthereof be- FIG. 2. As further shown in FIG. 2, an accumulator tank 37may be suitably mounted between the supporting plates 14 and 18, thisaccumulator being connected in communication with the incoming source ofhydraulic pressure fluid. Also, if desired, another accumulator tank maybe provided, as indicated at 38, connected in communication with theoutlet side of the hydraulic circuit, these accumulators servingfunctions similar to those described in the above-mentioned co-pendingapplication.

While with one embodiment of the hydraulic circuit arrangements inaccordance with the invention, a main cycling valve may be used, asindicated at 34, 34a in FIGS. 1 and 2, yet with other embodiments, forreasons hereinafter explained, it is desirable to provide a main cyclingvalve, located for example as shown at 40 in FIG. 2, in which case othervalves will operate as pilot valves.

Referring now to the schematic diagram of the hydraulic circuitarrangement of FIG. 3, certain of the parts as above referred to arehere identified by the same numerals, the piston in the hydrauliccylinder being shown at 41 on its downstroke, and the cam follower 29being shown in its position as swung to the right, where it remainsafter the cam 28 has started down and until the time of termination ofthe downstroke, whereupon the cycling valve is hydraulically operated ina direction to swing the cam follower 29 to the left in a position readyto be engaged by the cam 28 when the latter approaches the terminationof the upstroke again.

It will be understood that a suitable known form of power pack may beused to provide a source of hydra-ulic fluid under pressure to theintake conduit 42 of ing suitably connected (by means not shown) to ahamv mer ram 21. The upper and lower supporting plates 14 and 18 may besuitably connected by four tubes as at 22, 23, 24 and 25, welded attheir upper and lower ends respectively to the plates 14 and 18.

The construction as thus far described may be in accordance with priorknown practices, as disclosed in the U.S. patent of Ernst W. Spannhakeet al. No. 3,237,406, granted March 1, 1966, for example, from which itwill be noted that these hammers operate at speeds of about 100 blowsper minute or substantially in excess thereof, and have rams weighing5000 to 15,000 pounds or more. In hammers such as there disclosed, thelimits of the downward and upward strokes are controlled by mechanicallyoperating cycling valve means, actuated for example by avertically-extending actuating bar, like that here shown in FIGS. 1 and2 at 26, attached at its lower end to the ram and slidable in suitableguide means as at 27. In accordance with prior practices, such slide barmeans has been arranged to carry two cams, one for reversing the hammercycling valve near the end of the downstroke, and the other forreversing the valve near the end of the upstroke. But with the presentinvention, only one such cam is provided, viz. as shown at 28, forcontrolling the valve at or near the end of the upstroke, the cyclingvalve being hydraulically controlled at the end of the downstroke ashereinafter explained. As here shown, the cam 28 on the upstroke isadapted to engage a cam follower 29 pivoted about an axis at 30 andoperatively connected to the lever 31 and thence by a link 32 to the endof a valve-operating stem 33 of a cycling valve (or alternatively apilot valve) shown generally at 34, 34a (or a cycling valve as at 72 inFIG. 6), and the constructions and operation of which are furtherexplained below.

In case the hammer is to be mounted or carried as a part of a piledriving rig, the hammer assembly may be slidably mounted in verticalguide means, or verticallyextending so-called leads," as indicated at 35and 36 in the hydraulic circuit of FIG. 3, the release or drain conduitfor which is indicated at 43. As illustrated in this diagram, it will benoted that the fluid pressure is in communication with the accumulator37 and also (by way of a conduit 44) in communication through a valvepassage 45 and conduits 46 and 47 with the space above the piston 41,thus forcing the piston down. Although the pressure supply conduit 42 isalso in communication (by way of a conduit 48) with the space beneaththe piston, this does not prevent the piston from being forced down,because the effective pressure-receiving area on the underside of thepiston as compared with that on the upper side, is diminished by reasonof the cross-sectional area of the piston rod 20 (as is common with suchdifferential pistons).

Assuming now that before the piston reaches the lower end of thecylinder 12, the ram strikes a blow by engaging with whatever object isto receive an impact, then the above-referred-to water hammer effectwill take place, momentarily causing a sharp increase in the liquidpressure in the cylinder above the piston. Thus a substantial impulse ofincreased pressure will be conveyed through the conduit 47, to apressure release valve, as schematically indicated at 50, through aconnection 51, whereby, through a connection 52, pressure will beapplied to the hydraulically operated end 53 of the cycling valve 34,causing the valve spool therein to be thrust to the right. Thereupon avalve passage 54 will be brought into position to connect conduit 46 toan outlet conduit 55 connected to the drain conduit 43. Thus fluid willbe re leased from above the piston 41, allowing the pressure which isstill being maintained beneath the piston, to move the piston on itsupward stroke. At the same time, the shifting of the cycling valve 34toward the right will have moved the cam follower 29 to the positionshown in dotted lines, ready to be engaged by the cam 28 when theupstroke is about to be terminated. At termination of the upstroke, cam28 will operate the follower 29 to shift the cycling valve 34 back toits position for controlling the downstroke. The pressure which actuateddevice 53 will then be released through a check valve 50a.

In case the ram, during the lower part of the downstroke, does not meetwith any object to apply an impact thereto, such as would stop thedownstroke of the piston, then cushioning means for terminating thedownstroke may come into play, as will now be described. That is, thehydraulic pressure is applied to the space beneath the piston, as abovementioned, by way of a conduit 48 which is connected into the cylinderat an orifice 56 spaced somewhat above the bottomof the cylinder. Thuswhen the piston 41 moves down far enough to shut off orifice 56, therewill still remain a cushioning volume of liquid beneath the piston, andthe pressure in this volume will rapidly increase, thereby checking andstopping the movement of the piston before it can forcefully strike thebottom of the cylinder, or in any way cause destructive effects.However, the increase of pressure in this volume of liquid is kept frombecoming excessive by the provision of a throttling type of check valveat 57, having, if desired, an adjustable spring to permit adjustment ofthe rate of release of the excess pressure beneath the piston. It willbe noted that the throttling check valve 57 is connected by a conduit 58through an orifice 59 at the lower end. of the cylinder, so that suchexcess pressure within the bottom of the cylinder is released backthrough the check valve 57, and back into the pressure supply line 42.When the piston starts to rise again, and before it opens the orifice56, liquid is admitted thereunder through a check valve 60, positionedto admit pressure liquid from the supply lines 42, 48, through conduit58 into orifice 59. And, of course, after the piston passes up beyondorifice 56, liquid will continue to be admitted thereunder throughconnection 48.

It will be noted that a like cushioning arrangement is provided at thelower end of the cylinder in each of the other embodiments of theinvention, as illustrated in the diagrams of FIGS. 4, 5 and 6.

In some cases the downstroke of the piston may be terminated withinsufiicient abruptness to cause any substantial water hammer effect,for example the downstroke may be terminated by the above-describedcushioning arrangement, or by reason of the ram engaging some relativelysoft mass and becoming stopped, without being abruptly stopped. In suchcases, nevertheless, the cycling valve 34 will be caused to operate byreason of actuation of the pressure-release valve 59, for the reasonthat the power pack for supplying the hydraulic pressure to the systemwill ordinarily comprise positive displacement pumps connected into theclosed hydraulic system, whereby the power source continuing to supplyfluid will thereby raise the general level of the system pressure andactuate the cycling valve arrangement, so as to release the hydraulicpressure above the piston promptly following termination of itsdownstroke.

The basic principles of operation of the alternative embodiment of theinvention schematically illustrated in FIG. 4, are similar to thoseinvolved in FIG. 3. However, in FIG. 4 the valve 34a acts in effect as apilot valve, Where-as the valve shown at 40 constitutes the main cyclingvalve. It may be desirable to use the arrangement of FIG. 4 in case thequantity of fluid released through the release valve 50 is notsufl'ifiicient to cause actuation of the cycling valve 34 of FIG, 3. Insuch cases, the main cycling valve 40 may be used, accompanied by thepilot valve 34a, which is utilized to control fluid from the main supplyline, for hydraulically actuating the cycling valve 40. Also it may bedesirable to use an arrangement with the pilot valve of FIG. 4 to reducethe mechanical load and thereby to minimize wear of the cam mechanismand associated parts 2832.

In FIG. 4, the cycling valve 40 has a hydraulic actuator 6-1 for movingthe valve toward the left, and a hydraulic actuator 62 for moving thevalve toward the right. This valve has passages 63 and 64. Pilot valve34a has a hydraulic actuator 65 for moving this valve toward the right,its actuation toward the left being caused by the cam means 28, 29. Thispilot valve has passages 6 66, 67, 68 and 69. This valve, being in itsleft hand position during the downstroke of the hammer, the passage 68connects the source of pressure 42 to the actuator 62 of valve 40,holding the latter valve in its right hand position. Also, passage 69 ofvalve 34a connects hydraulic actuator 61 to the drain passage 43, thusreleasing the pressure in actuator 61 during the downstroke of thehammer.

' During the downstroke, passage 64 in valve 40, it will be noted,serves to connect the supply pressure from pressure inlet 42 andaccumulator 37 to the connection 47 running to the upper end of thehammer cylinder, connection 47 also having a branch'going to thepressure relief valve 50. At the time of termination of the downstroke,either the above-mentioned water hammer effect, or increased pressureconditions in the system, will serve to actuate pressure relief valve 54thereby admitting pressure to the hydraulic actuator 65 for valve 34a.This will cause the hydraulic circuit conditions to shift into accordwith the diag ram of FIG. 5. Here, it will be noted, passage 66 of valve3401 will serve to connect the source of pressure 42 to actuator 61 forvalve 40, thus moving that valve to the left, as shown in FIG. 5. Inthat position passage 63 of valve 40 serves to connect the outlet drainconduit 43 and outletaccumulator 38 to the conduit 47, thereby releasingpressure from the upper part of the hammer cylinder. At the same time,in valve 34a, passage 67 will serve to connect actuator 62 of valve 40to the outlet drain 43, thus releasing the pressure from actuator 62,permitting the valve 40 to move to the left as aforesaid. With thecircuit in this condition, the hammer piston will continue on itsupstroke until, at the proper time near the top of its stroke, cam 28will actuate follower 29, thereby shifting valve 34a to the left, thusrestoring conditions for the downstroke, as above described inconnection with FIG. 4. Other details as to the operation of thehydraulic circiuts of FIGS. 4 and 5 will be apparent from the abovedescription of FIG. 3.

Reference will now be made to FIG. 6, schematically showing thehydraulic circuit of the invention as applied in one of its forms to adouble-acting type of hydraulic hammer, wherein a cylinder 70 isschematically shown, having a piston 71 connected to the piston rod 20',this piston being adapted to be actuated on itsdownstroke by pressureabove the piston and during a time when pressure is released from belowthe piston, and the piston being adapted to operate on its upstroke whenpressure is applied under the piston and released from above the piston.P-arts'of FIG. 6 comparable to those of FIG. 3 are identified by thesame reference numerals, but here the passages of a cycling valve, shownat 72, are necessarily different. Valve 72 is moved to the right byhydraulic actuator 73, and the valve has passages 74, 75, 76 and 77.During the downstroke of the hammer, as shown in FIG. 6, valve 72 is inits lefthand position, having been moved to that position by the camfollower 29 just prior to the termination of the upstroke. With valve 72in this position, passage 76 therein connects the pressure source by wayof conduit 47 to the upper end of the cylinder 70. Meanwhile, the spacewithin the cylinder beneath piston 71 is in communication with theoutlet drain 43 by way of connection 78, passage 77 and conduit 79.Then, when the piston reaches the end of its downstroke with theresulting increased pressure conditions or water hammer effect above thepiston, this will actuate pressure release valve 50, which in turnapplies pressure to hydraulic actuator 73 for moving the cycling valvetowards the right. Thereupon passage 74 will connect the space above thepiston 71 to the outlet drain 43 and passage 75 will connect the spaceunder the piston 71 to the pressure source 42, thereby starting thehammer upstroke.

In a typical case for hydraulic hammer situations such as used in piledriving for example, the power pack constituting the source of pressuremay be such as normally to maintain an operating pressure in theneighborhood of 5000 lbs. per square inch and may have a relief valveset to release pressure at 6500 to 7000 lbs. per square inch, forexample, although normally the system will be so designed that duringthe downstroke of the hammer and prior to termination of the downstroke,the pressure supplied to the hydraulic system will be less than 6000lbs. per square inch. The pressure at which relief valve 50 may then beset to open Will be of the range of 6000 to 6200 lbs. per square inch.However, of course, these pressures are given merely by way of examples,since widely different pressures or pressure ranges may be desirable,depending upon the size and purposes of the hydraulic hammer.

In FIGS. 7 and 7A, a form of differential hydraulic hammer is shown of arelatively narrow and vertically elongated shape, adapted for useinternally, for example, of a metal pile shell or core, such as acorrugated pi-le shell indicated at 80, which has been driven into theearth, and which may contain a hollow mandrel, such as indicated at 81.Here the upper body portion of the hammer may include upper and lowersupporting plate structures, as at 14', 18, interconnected by suitableframe means 82, upon which may be carired (at the places indicated) apilot valve 34' or 34a and a cycling valve 40', these valves being forpurposes corresponding to the valves hereinabove referred to inconnection with the other embodiments. Here the cylinder 83, connectedto the underside of plate 18', contains a piston 84, connected to anelongated piston rod 85, extending and connected at its lower end to alarge ram as at 86, the ram at its upper position being adapted to becontained within a shielding chamber 87.

While there are various situations in which it is desirable to providesuch a hydraulic hammer for use internally of a shell or caisson or thelike, the particular example here shown in FIGS. 7 and 7A is welladapted for use in forming so-called bulb piles. For that purpose, theassembled shell 80 and mandrel 81 may be first driven down into theearth (as by a suitable mandrel), while the lower ends thereof areclosed (for example by a sheet metal disc), then a quantity of concretemix, preferably of a relatively dry consistency, is deposited in thebottom of the assembly. Then the hydraulic hammer assembly may belowered into place, as shown in FIGS. 7 and 7A, and so operated that theram 86 will pound the dry-mix concrete charge down into the earthbeneath the shell, and from time to time, as the driving proceeds,additional charges may be discharged into the shell assembly to passdown around the hammer and down beneath the ram, so that a bulbousformation of concrete as at 88 is finally developed beneath the pileshell. Thereupon the hollow mandrel 81 and the hammer may be removedfrom the shell 80 and the shell filled with concrete.

This provides a very efiicient, relatively inexpensive and rapid way offorming a concrete bulb-type pile, in that the successive charges of theconcrete dry pack mix may be pounded into place without the necessity ofremoving and replacing the ram and hammer assembly each time anadditional charge is to be supplied.

Although certain particular embodiments of the invention are hereindisclosed for purposes of explanation, further modifications thereof,after study of this specification, will be apparent to those skilled inthe art to which the invention pertains. Reference should accordingly behad to the appended claims in determining the scope of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. In combination with a high speed reciprocating hydraulic power hammerhaving a cylinder and operating piston: a source for supplying liquidunder pressure; valve means for controlling the admission of liquid fromsuch source into the cylinder space for subjecting the piston to apressure within a normal predetermined range for actuating the piston onits working stroke, said valve r 0 means being actuatable for thereaftercontrolling release of the liquid from said space upon the return strokeof the piston, such pressure in said space being subject to an abruptincrease causing a water hammer impulse upon stopping of the pistonmovement as the result of the striking of a heavy blow by the hammer;and means acting responsive to the kinetic energy of such impulse forcausing such valve actuation and consequent release of the liquid fromsaid space.

2. The combination as set forth in the foregoing claim 1 and in whichhydraulic cushioning means is associated with the cylinder at a positionat the region of the termination of the normal full working stroke ofthe piston for cushioning the stopping of the working stroke in theabsence of a prior heavy blow being made by the hammer.

3. The combination as set forth in the foregoing claim 1 and in whichsaid hammer and its operating parts, including said valve means,cylinder and piston, and a ram connected to the lower end of the pistonrod, all being arranged within the confines of a vertically elongatedcylindrical space, whereby the assembly is adapted to be lowered foroperation into a pile shell or the like.

4. In combination with a differential type hydraulic power hammer havinga cylinder and operating piston: a source for supplying liquid underpressure; valve means for controlling the admission of liquid from suchsource into the cylinder space above the piston for subjecting thepiston to a pressure within a normal predetermined range for actuatingthe piston on its working stroke; means for maintaining a differentialpressure beneath the piston for moving same on its return stroke, saidvalve means being actuatable for controlling release of the liquid fromsaid space upon such return stroke, such pressure in said space beingsubject to an abrupt increase causing a Water hammer impulse uponstopping of the piston movement as the result of the striking of a heavyblow by the hammer; and means acting responsive to the kinetic energy ofsuch impulse for causing such valve actuation and consequent release ofthe liquid from said space.

5. In combination with a high-speed reciprocating hydraulic pile drivinghammer having a cylinder and operating piston: a source for supplyingliquid under pressure; valve means including connections operablemechanicaliy responsive to piston movement for actuating the valve tocontrol the admission of liquid from such source into the cylinder spacefor subjecting the piston to a pressure within a normal predeterminedrange for actuating the piston on its Working stroke, said valve meansbeing reversely actuatable for thereafter controlling release of theliquid from said space upon the return stroke of the piston, suchpressure in said space being subject to an abrupt increase causing awater hammer impulse upon stopping of the Working stroke of the hammeras a result of an abruptly resisted blow; and means acting directlyresponsive to the kinetic energy of such impulse for causing suchreverse actuation of the valve and the consequent release of the liquidfrom said space.

6. The combination as set forth in the foregoing claim 5 and in whichthe hydraulic hammer is of the differential type, means being providedfor maintaining a differential pressure beneath the piston.

7. The combination as set forth in the foregoing claim 5 and in whichthe hydraulic power hammer is of the double-acting type.

8. In combination with a hydraulic power hammer having a cylinder andoperating piston: a source for supplying liquid normally maintainedunder a pressure within a predetermined range; a first valve meanshydraulically actuatable to either of two positions and which in oneposition is connected to admit liquid from such source into the cylinderunder such pressure for moving the piston on its Working stroke, saidvalve means when in a reverse position acting to release such liquid; apilot valve means hydraulically actuatable in one direction; meansconnected thereto for operating same in the opposite directionresponsive to movement of the piston to the region of termination of itsreturn stroke; and a pressure release valve actuatable responsive to asubstantial increase above said normal pressure range of the operatingpressure in said cylinder upon the stopping of the working stroke of thepiston, said pressure release valve being connected then to actuatehydraulically said pilot valve, whereupon the latter becomes connectedto move said first valve means to its reversed position, thereby toterminate the Working stroke.

9. In combination with a hydraulic power hammer of the differential typehaving a cylinder and operating piston: a source for supplying liquidnormally maintained under a pressure within a predetermined range, thelower end of the cylinder being connected to such source; a first valvemeans hydraulically actuatable to either of two positions and which inone position is connected to admit liquid from such source into theupper end of the cylinder under such pressure for moving the piston onits Working stroke, said valve means when in a reverse position actingto release such liquid from the upper end of the cylinder; a pilot valvemeans hydraulically actuatable in one direction; means connected theretofor operating same in the opposite direction (responsive to movement ofthe piston to the region, of termination of its return stroke; and apressure release valve actuatable responsive to a substantial increaseabove said normal pressure range of the operating pressure in the upperend of the cylinder upon the stopping of the working stroke of thepiston, said pressure release valve being connected then to actuatehydraulically said pilot valve, whereupon the latter becomes connectedto move said first valve means to its reversed position, thereby toterminate the working stroke.

References Cited by the Examiner FRED C. MATTERN, JR., Primary Examiner.

MILTON KAUFMAN, Examiner.

L. P. KESSLER, Assistant Examiner.

1. IN COMBINATION WITH A HIGH SPEED RECIPROCATING HYDRAULIC POWER HAMMERHAVING A CYLINDER AND OPERATING PISTON: A SOURCE FOR SUPPLYING LIQUIDUNDER PRESSURE; VALVE MEANS FOR CONTROLLING THE ADMISSION OF LIQUID FORMSUCH SOURCE INTO THE CYLINDER SPACE FOR SUBJECTING THE PISTON TO APRESSURE WITHIN A NORMAL PREDETERMINED RANGE FOR ACTUATING THE PISTON ONITS WORKING STROKE, SAID VALVE MEANS BEING ACTUATABLE FOR THEREAFTERCONTROLLING RELEASE OF THE LIQUID FROM SAID SPACE UPON THE RETURN STROKEOF THE PISTON, SUCH PRESSURE IN SAID SPACE BEING SUBJECT TO AN ABRUPTINCREASE CAUSING A WATER HAMMER IMPULSE UPON STOPPING OF THE PISTONMOVEMENT AS THE RESULT OF THE STRIKING OF A HEAVY BLOW BY THE HAMMER;AND MEANS ACTING RESPONSIVE TO THE KINETIC ENERGY OF SUCH IMPULSE FORCAUSING SUCH VALVE ACTUATION AND CONSEQUENT RELEASE OF THE LIQUID FROMSAID SPACE.